Immunologic response to oral polio vaccine in human immunodeficiency virus-infected and uninfected Zimbabwean children

Impaired functionality of antigen presenting cells in HIV- exposed uninfected infants in the first six months of life

HIV-exposed uninfected infants (HEU) have increased morbidity and mortality due to infections in the first 6 months of life that tapers down to 2 years of life. The underlying immunologic defects remain undefined. We investigated antigen-presenting cells (APC) by comparing the phenotype of unstimulated APC, responses to toll-like receptor (TLR) stimulation, and ability to activate natural killer (NK) cells in 24 HEU and 64 HIV-unexposed infants (HUU) at 1-2 days of life (birth) and 28 HEU and 45 HUU at 6 months of life. At birth, unstimulated APC showed higher levels of activation and cytokine production in HEU than HUU and stimulation with TLR agonists revealed lower expression of inflammatory cytokines and activation markers, but similar expression of IL10 regulatory cytokine, in APC from HEU compared to HUU. Differences were still present at 6 months of life. From birth to 6 months, APC underwent extensive phenotypic and functional changes in HUU and minimal changes in HEU. TLR stimulation also generated lower NK cell expression of CD69 and/or IFNγ in HEU compared with HUU at birth and 6 months. In vitro experiments showed that NK IFNγ expression depended on APC cytokine secretion in response to TLR stimulation. Ex vivo IL10 supplementation decreased APC-mediated NK cell activation measured by IFNγ expression. We conclude that APC maturation was stunted or delayed in the first 6 months of life in HEU compared with HUU. Deficient inflammatory APC responses and/or the imbalance between inflammatory and regulatory responses in HEU may play an important role in their increased susceptibility to severe infections.

Pediatric HIV Infection and Decreased Prevalence of OPV Point Mutations Linked to Vaccine-associated Paralytic Poliomyelitis

Background

Mutations associated with prolonged replication of the attenuated polioviruses found in oral poliovirus vaccine (OPV) can lead to vaccine-derived poliovirus (VDPV) and cause paralysis indistinguishable from that caused by wild poliovirus. In response, the World Health Organization has initiated the transition to exclusive use of inactivated poliovirus vaccine (IPV), with OPV administration in cases of outbreak. However, it is currently unclear how IPV-only vaccination, well known to provide humoral but not mucosal immunity, will impact the development of paralysis causing OPV variants. Children infected with human immunodeficiency virus (HIV) have been documented to show decreased mucosal immunity following OPV vaccination. Thus, HIV-infected children vaccinated with OPV may serve as proxy for children with IPV-only vaccination.

Methods

We conducted a prospective study of Zimbabwean infants receiving OPV as part of their routine vaccination schedule. Stool samples collected from OPV-vaccinated children serially until age 24 months were tested for OPV serotypes using a real-time polymerase chain reaction protocol that quantifies the amount of mutant OPV variants found in each sample.

Results

Out of 2130 stool samples collected from 402 infants 365 stool samples were OPV positive: 313 from 212 HIV-noninfected (HIV−) infants and 52 from 34 HIV-infected (HIV+) infants. HIV− infants showed significantly higher proportions of OPV mutants when compared to HIV+ infants.

Conclusions

HIV infection is associated with a reduced proportion of OPV vaccine associated paralytic polio mutants. These results suggest that OPV administered to individuals previously vaccinated only with IPV will show decreased propensity for OPV mutations.

Six-monthly palivizumab prophylaxis effectively reduced RSV-associated hospitalization rates of preterm infants in a subtropical area: a population-based cohort study

BACKGROUND

To evaluate the effects of 6-monthly palivizumab on respiratory syncytial virus-associated hospitalization (RSVH) in preterm infants in an area without RSV seasonality.

METHODS

RSV prophylaxis with 6-monthly palivizumab in infants born at gestational age (GA) ≤28 weeks or those born at GA 29-35 weeks with bronchopulmonary dysplasia (BPD) was implemented in Taiwan since 2010. RSVH, use of mechanical ventilation (MV), admission to intensive care unit (ICU), length of hospital stay, and annual mortality were compared between the historical control group (no prophylaxis, 2008-2009) and the prophylaxis group (2011-2013).

RESULTS

The annual RSVH rates decreased in the target population and in subgroups of infants who received prophylaxis (all target infants: odds ratio [OR], 0.43; 95% confidence interval [CI], 0.29-0.65). No difference was observed in MV and ICU usage and 1-year mortality in the ≤28 weeks subgroup. In the GA 29-35 weeks with BPD subgroup, ICU usage and 1-year mortality rates were significantly reduced with palivizumab prophylaxis regimen. A significant decrease was noted in the annual mortality and ICU admission rates of infants who received prophylactic treatment.

CONCLUSION

Six-monthly palivizumab treatment reduced the RSVH rate, ICU usage, and annual mortality rates of target infants in an area without RSV seasonality.

HIV-Exposed Uninfected Infants Have Increased Regulatory T Cells That Correlate With Decreased T Cell Function

Background: HIV-exposed uninfected infants (HEU) are at higher risk of severe infections, hospitalizations and death compared with HIV-unexposed uninfected infants (HUU), but the immune deficit underlying it is not known. To address this gap, we investigated T cell functionality and its relationship to phenotypic profiles of T cells and antigen presenting cells (APC) in HEU and HUU.

Methods: Blood mononuclear cells from 55 HEU and 16 HUU were stimulated with Staphylococcal Enterotoxin B (SEB) or mock for 72 h, and tested by flow cytometry for proliferation and expression of Th1, Th2, and regulatory (Treg) markers. In parallel, cells were phenotypically assessed for differentiation profiles of Treg, conventional T cell (Tconv) and APC in unstimulated cells.

Results: HEU had lower CD4+ functional responses to SEB/mock and similar CD8+ responses compared with HUU. In the phenotypic T cell panel, HEU showed higher proportions of CD4+ and CD8+ Treg expressing IL10, FOXP3, and CD25; higher effector Tconv and Treg; and lower naïve and CD4+TGFβ+ Treg compared with HUU. In the phenotypic APC panel, HEU showed higher proportions of CD1c+ cDC2, CD123+ pDC, CD16+ inflammatory monocytes and cDC and higher expression of CD103 on CD1c-CD123-CD16-cDC1 compared with HUU. Regression analyses adjusted for HIV exposure and multiple comparisons showed that higher CD8+IL10+ and CD8+FOXP3+ Treg in unstimulated cells were associated with lower CD8+ T cell functional responses to SEB/mock. Functionality was not affected by Tconv differentiation, but higher APC activation in aggregate was associated with higher CD8+IL10+ Treg responses to SEB.

Conclusions: T cell functionality was decreased in HEU compared with HUU. High CD8+ Treg proportions were the most important predictors of decreased T cell functionality in HEU and HUU.

B and T Cell Phenotypic Profiles of African HIV-Infected and HIV-Exposed Uninfected Infants: Associations with Antibody Responses to the Pentavalent Rotavirus Vaccine

We examined associations between B and T cell phenotypic profiles and antibody responses to the pentavalent rotavirus vaccine (RV5) in perinatally HIV-infected (PHIV) infants on antiretroviral therapy and in HIV-exposed uninfected (PHEU) infants enrolled in International Maternal Pediatric Adolescent AIDS Clinical Trials P1072 study (NCT00880698). Of 17 B and T cell subsets analyzed, PHIV and PHEU differed only in the number of CD4+ T cells and frequency of naive B cells, which were higher in PHEU than in PHIV. In contrast, the B and T cell phenotypic profiles of PHIV and PHEU markedly differed from those of geographically matched contemporary HIV-unexposed infants. The frequency of regulatory T and B cells (Treg, Breg) of PHIV and PHEU displayed two patterns of associations: FOXP3+ CD25+ Treg positively correlated with CD4+ T cell numbers; while TGFβ+ Treg and IL10+ Treg and Breg positively correlated with the frequencies of inflammatory and activated T cells. Moreover, the frequencies of activated and inflammatory T cells of PHIV and PHEU positively correlated with the frequency of immature B cells. Correlations were not affected by HIV status and persisted over time. PHIV and PHEU antibody responses to RV5 positively correlated with CD4+ T cell counts and negatively with the proportion of immature B cells, similarly to what has been previously described in chronic HIV infection. Unique to PHIV and PHEU, anti-RV5 antibodies positively correlated with CD4+/CD8+FOXP3+CD25+% and negatively with CD4+IL10+% Tregs. In conclusion, PHEU shared with PHIV abnormal B and T cell phenotypic profiles. PHIV and PHEU antibody responses to RV5 were modulated by typical HIV-associated immune response modifiers except for the association between CD4+/CD8+FOXP3+CD25+Treg and increased antibody production.

Vaccinations for the HIV-Infected Adult: A Review of the Current Recommendations, Part II

Vaccination is a critical component for ensuring the ongoing health HIV-infected adults. Since this group may have reduced immune responses and shorter durations of protection post-vaccination, HIV-specific guidelines have been published. This review article provides a comprehensive discussion of the current guidelines and evidence-based data for vaccinating HIV-infected adults, including data on dosing schedules, immunogenicity studies, and safety. In the current paper, part II of the review, live vaccines, as well as vaccines for travelers and specific occupational groups, will be discussed.

Enteroviruses and Parechoviruses

Infections with enteroviruses and human parechoviruses are highly prevalent, particularly in neonates, where they may cause substantial morbidity and mortality. Individuals with B-cell-related immunodeficiencies are at risk for severe enteroviral infections, usually a chronic and fatal meningoencephalitis. In transplant recipients and patients with malignancy, enterovirus infections typically involve the respiratory tract, but cases of severe, disseminated infection have been described. The mainstay of diagnosis for enterovirus and human parechovirus infections involves the use of molecular diagnostic techniques. However, routine nucleic acid-detection methods for enteroviruses will not detect human parechoviruses. Laboratory diagnosis of these viral infections is important in determining a patient's prognosis and guiding clinical management.

Safety and immunogenicity of a live attenuated pentavalent rotavirus vaccine in HIV-exposed infants with or without HIV infection in Africa

OBJECTIVE

Although many HIV-infected (HIV+) and HIV-exposed but uninfected (HEU) infants have received live rotavirus vaccines since the WHO recommended universal administration of these vaccines to infants, there has been limited prospective information on their safety and immunogenicity in either group of infants.

DESIGN/METHODS

We performed a randomized, double-blinded, placebo-controlled trial of the safety and immunogenicity of oral pentavalent rotavirus vaccine (RV5) administered to HIV+ and HEU infants in four African countries. Ninety-three percent of HIV+ infants were receiving antiretroviral therapy prior to vaccination. Participants were followed for safety. Immune responses were measured 14 days after three doses of RV5, including serum antirotavirus neutralizing and IgA antibodies, IgA antibody in stool, and antirotavirus memory B and T-cell FluoroSpot. Shedding of RV5 in stool was monitored.

RESULTS

A total of 76 HIV+ and 126 HEU infants were enrolled from 2009 to 2013. No significant differences were found in adverse event rates, including grade 3 events, between RV5 and placebo recipients, for either HIV+ or HEU infants. The proportion of antirotavirus IgA responders (at least three-fold increase from baseline) after RV5 administration was 81% in both HIV+ and HEU infants, which was approximately 2.5-fold higher than in placebo recipients (P < 0.001). Neutralizing antibody responses to three of five serotypes were significantly higher after RV5 regardless of HIV status, and those of HIV+ infants were equal or greater than responses of HEU infants to all five serotypes. Only one HIV+ RV5 recipient had RV5 isolated from stool.

CONCLUSION

RV5 was immunogenic in both HIV+ and HEU infants and no safety signals were observed.

Poliovirus immunity among pregnant females aged 15-44 years, Namibia, 2010

BACKGROUND

Poliovirus (PV) antibody seroprevalence studies assess population immunity, verify an immunization program's performance and vaccine efficacy, and guide polio eradication strategy. Namibia experienced a polio outbreak among adults in 2006, yet population seroimmunity was unknown.

METHODS

We tested 2061 specimens from Namibian pregnant females aged 15-44 years for neutralizing antibody to PV types 1-3 (PV1-3); all females were sampled during the 2010 National HIV Sentinel Survey. We determined the proportion of females seropositive for PV antibody by 5-year age strata, and analyzed factors associated with seropositivity, including age, gravidity, human immunodeficiency virus (HIV) infection status, residence, and antiretroviral treatment, by log-binomial regression.

RESULTS

The seroprevalence was 94.6% for PV1, 97.0% for PV2, and 85.1% for PV3. HIV-positive females had significantly lower seroprevalence than HIV-negative females for PV1 (91.8% vs 95.3%; P<.01) and PV3 (80.0% vs 86.1%; P<.01) but not for PV2 (96.4% vs 97.1%; P=.3). The prevalence ratio of seropositivity for HIV-positive females versus HIV-negative females was 0.95 (95% confidence interval [CI], .92-.98) for PV1, 0.99 (95% CI, .97-1.01) for PV2, and 0.92 (95% CI, .87-.96) for PV3.

CONCLUSIONS

Despite relatively high PV seroprevalence, Namibia might remain at risk for a PV outbreak, particularly in lower-seroprevalence populations, such as HIV-positive females. Namibia should continue to maintain high routine polio vaccination coverage.

Respiratory syncytial virus circulation in seven countries with Global Disease Detection Regional Centers

BACKGROUND

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections in young children globally, with the highest burden in low- and middle-income countries where the association between RSV activity and climate remains unclear.

METHODS

Monthly laboratory-confirmed RSV cases and associations with climate data were assessed for respiratory surveillance sites in tropical and subtropical areas (Bangladesh, China, Egypt, Guatemala, Kenya, South Africa, and Thailand) during 2004-2012. Average monthly minimum and maximum temperatures, relative humidity, and precipitation were calculated using daily local weather data from the US National Climatic Data Center.

RESULTS

RSV circulated with 1-2 epidemic periods each year in site areas. RSV seasonal timing and duration were generally consistent within country from year to year. Associations between RSV and weather varied across years and geographic locations. RSV usually peaked in climates with high annual precipitation (Bangladesh, Guatemala, and Thailand) during wet months, whereas RSV peaked during cooler months in moderately hot (China) and arid (Egypt) regions. In South Africa, RSV peaked in autumn, whereas no associations with seasonal weather trends were observed in Kenya.

CONCLUSIONS

Further understanding of RSV seasonality in developing countries and various climate regions will be important to better understand the epidemiology of RSV and for timing the use of future RSV vaccines and immunoprophylaxis in low- and middle-income countries.

Vaccine poliovirus shedding and immune response to oral polio vaccine in HIV-infected and -uninfected Zimbabwean infants

BACKGROUND

With prolonged replication, attenuated polioviruses used in oral polio vaccine (OPV) can mutate into vaccine-derived poliovirus (VDPV) and cause poliomyelitis outbreaks. Individuals with primary humoral immunodeficiencies can become chronically infected with vaccine poliovirus, allowing it to mutate into immunodeficiency-associated VDPV (iVDPV). It is unclear if children perinatally infected with the human immunodeficiency virus (HIV), who have humoral as well as cellular immunodeficiencies, might be sources of iVDPV.

METHODS

We conducted a prospective study collecting stool and blood samples at multiple time points from Zimbabwean infants receiving OPV according to the national schedule. Nucleic acid extracted from stool was analyzed by real-time polymerase chain reaction for OPV serotypes.

RESULTS

We analyzed 825 stool samples: 285 samples from 92 HIV-infected children and 540 from 251 HIV-uninfected children. Poliovirus shedding was similar after 0-2 OPV doses but significantly higher in the HIV-infected versus uninfected children after ≥ 3 OPV doses, particularly within 42 days of an OPV dose, independent of seroconversion status. HIV infection was not associated with prolonged or persistent poliovirus shedding. HIV infection was associated with significantly lower polio seroconversion rates.

CONCLUSIONS

HIV infection is associated with decreased mucosal and humoral immune responses to OPV but not the prolonged viral shedding required to form iVDPV.

Immune responses and protection in children in developing countries induced by oral vaccines

Oral mucosal vaccines have great promise for generating protective immunity against intestinal infections for the benefit of large numbers of people especially young children. There however appears to be a caveat since these vaccines have to overcome the inbuilt resistance of mucosal surfaces and secretions to inhibit antigen stimulation and responses. Unfortunately, these vaccines are not equally immunogenic nor protective in different populations. When compared to industrialized countries, children living in developing countries appear to have lower responses, but the reasons for these lowered responses are not clearly defined. The most likely explanations relate to undernutrition, micronutrient deficiencies, microbial overload on mucosal surfaces, alteration of microbiome and microbolom and irreversible changes on the mucosa as well as maternal antibodies in serum or breast milk may alter the mucosal pathology and lower immune responses to interventions using oral vaccines. The detrimental effect of adverse environment and malnutrition may bring about irreversible changes in the mucosa of children especially in the first 1000 days of life from conception to after birth and up to two years of age. This review aims to summarize the information available on lowered immune responses to mucosal vaccines and on interventions that may help address the constraints of these vaccines when they are used for children living under the greatest stress and under harmful adverse circumstances.

Vaccines against mucosal infections

There remains a great need to develop vaccines against many of the pathogens that infect mucosal tissues or have a mucosal port of entry. Parenteral vaccination may protect in some instances, but usually a mucosal vaccination route is necessary. Mucosal vaccines also have logistic advantages over injectable vaccines by being easier to administer, having less risk of transmitting infections and potentially being easier to manufacture. Still, however, only relatively few vaccines for human use are available: oral vaccines against cholera, typhoid, polio, and rotavirus, and a nasal vaccine against influenza. For polio, typhoid and influenza, in which the pathogens reach the blood stream, there is also an injectable vaccine alternative. A problem with available oral live vaccines is their reduced immunogenicity when used in developing countries; for instance, the efficacy of rotavirus vaccines correlates closely with the national per capita income. Research is needed to define the impact of factors such as malnutrition, aberrant intestinal microflora, concomitant infections, and preexisting immunity as well as of host genetic factors on the immunogenicity of these vaccines.